Hemodynamic effects of prenalterol in patients with ischemic heart disease and congestive cardiomyopathy.

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Abstract
The hemodynamic effects of a new .beta.1-agonist, prenalterol, were studied in 13 patients with severe left ventricular failure (New York Heart Association functional class III or IV). Seven patients had ischemic heart disease and 6 congestive cardiomyopathy. Left ventricular function was studied by catheter-tip manometer measurements of left ventricular pressure and simultaneous pressure-volume analysis. To minimize rate-related changes in left ventricular function, studies were performed during constant atrial pacing at 100 beats/min unless the intrinsic heart rate was higher. A 12-mg i.v. dose of prenalterol was infused. The maximum rate of pressure development (peak positive dP/dt) increased from 1084 .+-. 95 mm Hg/s (mean .+-. SEM [standard error of the mean]) to 1493 .+-. 176 mm Hg/s (P < 0.005). Stroke volume and ejection fraction also increased. Left ventricular relaxation, measured as the maximum rate of pressure fall (peak negative dP/dt) improved from -1011 .+-. 91 to -1202 .+-. 119 mm Hg/s. Alteration in the time constant of pressure fall (T) also suggested improved relaxation, as it decreased from 71.8 .+-. 7.7 to 48.5 .+-. 6.3 ms. Prenalterol also decreased left ventricular stiffness, particularly in patients with very stiff ventricles. As a positive inotropic agent, prenalterol increased left ventricular mean power from 5.2 .+-. 0.4 to 6.8 .+-. 0.7 W and left ventricular stroke work from 8.3 .+-. 0.7 to 10.2 .+-. 1.0 W-s (P < 0.005). Left ventricular stress did not change significantly. The ratio of the diastolic pressure-time index to the systolic pressure-time index increased significantly (0.53 .+-. 0.04 and 0.63 .+-. 0.04, reespectively, P < 0.005). Despite different absolute values, the percent changes of left ventricular function were similar in both groups. Even in patients with severe left ventricular failure, ventricular systolic and diastolic function can be improved by prenalterol. As a result of improved contractility, relaxation and stiffness, left ventricular filling pressure decreased. The data indicate a favorable effect on the balance between myocardial O2 supply and demand. Prenalterol (i.v.) is a promising new drug for patients with severe heart failure.